Morphometry of the fibular collateral ligament: anatomic study with comprehensive review of the literature.

There is no consensus in the literature related to the morphology, bony attachments, and variations of the fibular collateral ligament (FCL) of the knee. Our purpose was to investigate FCL morphology and to review reports in the literature regarding this structure. Seventy knees from formalin-fixed, adult cadavers were dissected and a digital caliper was used to measure FCL length, width, distance from proximal attachment to articular surface (PA→AS), and distance from distal attachment to articular surface (DA→AS). The mean (SE) length and width of all FCLs was 48.3 (1.1) mm and 4 (0.16) mm, respectively. The mean (SE) PA→AS and DA→AS of all FCLs was 22 (0.8) mm and 24.8 (1) mm, respectively. We found a direct relationship between the PA→AS and DA→AS distances (Spearman rho = 0.527, P = 0.002) and this association was independent of age and sex. Two FCL variations were found: a bifurcate ligament with two distal bands and a trifurcate ligament with three distal bands, all of which attached to the fibular head. Our literature review revealed that only 2/10 cadaveric FCL morphology studies reported variations similar to the current study. Further, there was variability in the reported location of the FCL proximal attachment. When combining our data with these studies, 105/219 FCLs directly attached to the apex of the lateral epicondyle (LE), 10/219 to a fovea posterior to the LE, and 104/219 posterior and proximal to the LE. These data may have implications related to FCL injury and repair.